The investigation of Cr deposition and poisoning effect on Sr-doped lanthanum manganite cathode induced by cathodic polarization for intermediate temperature solid oxide fuel cell

The impact of current density on Cr-poisoning of Sr-doped lanthanum manganite cathode is studied at 750 °C. The presences of SUS430 interconnect alloys cause rapid degradation in LSM cathode performance. The Cr deposits can be found not only on the LSM surface close to the electrode/electrolyte interface, but also on the YSZ surface. The deposition area is reach to 4.1 μm from the electrode/electrolyte interface after cathodic polarization with a current density of 400 mA cm−2 for 1200 min. TEM results clearly demonstrate that the particles on LSM surface are MnCr2O4 spinels, which means that the Cr species would react with Mn from LSM and then lead to the structural damages of LSM cathode. A high polarization current of 800 mA cm−2 significantly accelerates Cr deposition process, resulting in a wider deposition area of 5.9 μm on LSM surface. The present results show that the Cr deposition occurs beyond the electrolyte/electrode interface, which reveals that the deposition of Cr species is driven by chemical reaction, not electrochemical reduction. Cr species are induced to deposit on LSM cathode surface by chemical reaction with Mn2+ ions, and extend to YSZ surface under cathodic current.